Arc Welding Control for Zinc-Coated Steel Plate Defects
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Solution Overview
Problem
Conventional arc welding methods for zinc-coated steel plates result in defects like pits and blowholes, and excessive spatters due to the vaporization of zinc during welding, which compromises the strength of the welded structure and increases spatter generation.
Innovation Solution
The method involves alternating short circuit and arc periods with a steep increase in welding current gradient (at least 750 A/msec) and a first welding current of 300 A or higher, followed by a decrease in current upon constriction detection, and periodic changes in wire feeding speed to control the arc force and molten pool movement, effectively exposing the zinc vaporization area and reducing spatter generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If conventional arc welding method with mild current increase gradient is used, then spatter generation is suppressed, but zinc vapor cannot sufficiently escape causing blowholes and pits
Solution Approach 1:
The welding current is controlled to periodically alternate between a short-circuit period (low current) and an arc period (high current). During the arc period, the current increases with a gradient of 750 A/msec or more, creating strong arc force that pushes zinc vapor out of the molten pool. This periodic action between short-circuit and arc states enables effective zinc vapor escape while maintaining weld quality.
Solution Approach 2:
The invention changes the current increase gradient parameter from the conventional mild gradient to a steep gradient of 750 A/msec or more. This parameter change creates sufficient arc force during the arc period to generate strong molten pool movement and expose the zinc vaporization area, allowing zinc vapor to escape effectively and preventing blowholes and pits.
2Manufacturing precision
If steep current increase gradient (750 A/msec or more) is applied, then zinc vapor can escape effectively, but molten pool becomes unstable causing spatters
Solution Approach 1:
The welding process alternates between short-circuit period and arc period. During the short-circuit period, the current is low which stabilizes the molten pool. During the arc period, the current increases steeply (750 A/msec or more) to create arc force for zinc vapor escape. This periodic alternation allows the system to benefit from both low current stability and high current vapor escape capability.
Solution Approach 2:
Before applying the steep current increase gradient, the system first enters a short-circuit period where the current is kept low. This preliminary low-current state stabilizes the molten pool and prepares it for the subsequent steep current increase, preventing immediate spatter generation when the high current is applied.
3Productivity
If high welding current is maintained continuously, then welding speed increases, but zinc vapor accumulates causing blowholes and pits
Solution Approach 1:
Instead of maintaining high welding current continuously, the system uses periodic alternation between short-circuit period (low current) and arc period (high current). During the arc period, the high current provides sufficient heat for welding and creates arc force for zinc vapor escape. During the short-circuit period, the low current allows molten pool stabilization. This periodic pattern achieves both high welding speed and effective zinc vapor escape.
Solution Approach 2:
The alternating short-circuit and arc periods ensure continuous useful action: the arc period provides heat input and arc force for zinc vapor escape, while the short-circuit period provides molten pool stability. This continuous alternation ensures that zinc vapor is consistently pushed out during arc periods while the molten pool remains stable during short-circuit periods, preventing defect formation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach significantly minimizes defects such as pits and blowholes, suppresses spatter generation, and enhances welding quality by ensuring efficient zinc vapor release and stable molten pool movement.
Implementation Method 1
an arc is generated after release of the short circuit
Implementation Method 2
zinc of zinc coating 10 vaporizes and the zinc vapor leaves from root section 11 via the molten pool for the outside
Data Source
Figure 1
Figure 2A~2B
Figure 2C~2D
AI summary
As a conventional problem, welding on surface-treated material, such as a zinc-coated steel plate, considerably generates air holes including blowholes and also generates lots of spatters. Present invention provides a method of controlling arc welding performed in a manner that a short-circuit period, in which a short circuit is generated between a welding wire and an object to be welded, and an arc period, in which an arc is generated after release of the short circuit, are repeated alternately. According to the method, welding current is increased from an arc-regeneration-before current to a first welding current at a detection of release of the short circuit such that an increase gradient of the welding current becomes not less than 750A/msec. This suppresses generation of air holes and spatters in welding work on a surface-treated material, such as a zinc-coated steel plate.